More information about hearing aid compatibility can be found at the FCC’s website: http://www.fcc.gov/cgb/consumerfacts/hac_wireless.html.
There are two sets of standards for compatibility of digital wireless phones with hearing aids. These standards are established by the American National Standard Institute (ANSI): an “M” rating from one to four for reduced radio frequency (RF) interference to enable acoustic coupling with hearing aids that do not operate in telecoil mode, and a “T” rating from one to four to enable inductive coupling with hearing aids operating in telecoil mode.
Phones with an M-Rating of M3 or M4 meet FCC requirements. M4 is the better/higher of the two ratings.
Hearing devices may also be rated for this type of interference but your hearing device manufacturer or hearing health professional will be able to assist you with gathering information about your hearing device.
Phones with a T-Rating of T3 or T4 meet FCC requirements and are more likely to work well for people who use hearing aids with telecoils. In this rating scale, T4 is the better/higher of the two ratings.
GCI defines the level of a phone’s functionality with the following phone types:
Rugged – Basic functionality, talk and text, more durable housing, some are waterproof or water resistant
Talk and Text – Voice services and texting capability
Smartphone – Talk and text, feature phone, web browsing